Surreyadministrative and historic county of southeastern England, just southwest of London, adjoining the River Thames. The county consists of lowland crossed by two east-west ridges—the chalk hills of the North Downs just south of the Thames valley and, farther south, a band of lower greensand rocks, which includes the highest point in the county, Leith Hill (965 feet [294 m]). The two ridges, with their intervening vale and the gaps cut in them by such rivers as the Mole and the Wey, give the county a variety of landscapes, and in 1958 some 160 square miles (415 square km) of southern Surrey were officially designated as an Area of Outstanding Natural Beauty. Interspersed among these natural areas are suburban areas linked economically with neighbouring London.

The administrative county comprises 11 districts: Mole Valley and Tandridge and the boroughs of Elmbridge, Epsom and Ewell, Guildford, Reigate and Banstead, Runnymede, Spelthorne, Surrey Heath, Waverley, and Woking. The administrative county of Surrey occupies a considerably smaller area than the historic county. The northeastern part of the historic county now lies within the metropolitan county of Greater London, forming all or most of the boroughs of Croydon, Kingston-upon-Thames, Lambeth, Merton, Richmond-upon-Thames, Southwark, Sutton, and Wandsworth. This history accounts for the location of the county’s administrative centre in the London borough of Kingston-upon-Thames. In addition, a small part of the historic county of Surrey, including Gatwick Airport and its immediate environs, lies within the borough of Crawley in the administrative county of West Sussex. While these parts of other administrative units belong to the historic county of Surrey, the borough of Spelthorne, though assigned to the administrative county of Surrey, forms part of the historic county of Middlesex.

Archaeological finds provide evidence of human occupation in the historic county of Surrey dating to Palaeolithic times. The area appears to have been relatively thinly populated during the Roman and early Saxon periods. Chertsey Abbey, founded in 666, had large landholdings across the county, and after 1066 large parts of the county belonged to the Norman nobility. Southwark, linked with London by the London Bridge, became an important ecclesiastical centre, and Kingston-upon-Thames was an important medieval market town.

In the Middle Ages sheep raising was an important activity, and by the 16th century a cloth trade was also growing at Guildford, Godalming, and Farnham. Market gardens, too, became significant in the north and west. The forested hills, sparsely populated until the 19th century, served two main purposes: as hunting preserves (Henry VIII, for example, built a flamboyant hunting lodge at Nonsuch Park) and as a source of timber for charcoal (used in iron smelting and gunpowder production), construction, and shipbuilding.

Transport of these products, originally dependent on rivers, was facilitated after 1800 by the construction of railways. The Surrey Iron Railway from Wandsworth to Merstham, worked by horses, was the first public railway sanctioned by the British Parliament (1801). During the 19th century, Surrey acquired the densest network of suburban railways anywhere in the world, originating at seven terminal stations in London and covering northern Surrey. Suburban growth, which had begun in Southwark during the Middle Ages, spread along the railway lines virtually unchecked until World War II. In 1889, the present-day boroughs of Southwark, Lambeth, and Wandsworth were incorporated into the new administrative county of London. After World War II growth continued but under planning restraints, including strict controls in London’s Greenbelt and the designated area of natural beauty. In 1965, the boroughs of Croydon, Kingston-upon-Thames, Merton, Richmond-upon-Thames, and Sutton became part of the new metropolitan county of Greater London. Area, administrative county, 645 642 square miles (1,670 663 square km). Pop. (1998 2005 est.) , administrative county, 1,060075,500.